Measuring the properties of dark energy and dark matter with strong gravitational lensing and stellar dynamics

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Our Universe contains two mysterious substances: dark energy and dark matter. Dark matter isneeded to explain the orbital speeds of stars within galaxies, and dark energy explains the surprisingobservation that the Universe's expansion is speeding up. In this project we will combine HubbleSpace Telescope observations of strong gravitational lensing and Very Large Telescope observationsof the orbital properties of stars to constrain the properties of both dark matter and dark energy.Gravitational lensing occurs due to the warping of space time around massive galaxies. As light froma background galaxy pass by a foreground galaxy its path is deflected, and in some cases thedeflection is large enough that multiple images of the background source is observed. These rarealignments are called strong lenses and the separation between the images is sensitive to dark matterin the lensing galaxy and the dark energy between us and the source. However these properties aredegenerate, and only by combining with external data can we disentangle the effects of dark matter,dark energy and gravity. We will use the orbital properties of stars within the lens galaxy to break thisdegeneracy: as the mass of the galaxy increases, the stars orbit faster.